Rami Arieli: "The Laser Adventure" Chapter 1.1 page 4
The electromagnetic spectrum
Figure 1.4 describes the electromagnetic spectrum.
Each part of the spectrum has a common name, and its range of wavelengths, frequencies and energies.
The borders between the ranges are not sharp and clear, but are defined according to the applications of radiation in that portion of the spectrum.

Figure 1.4: The Electromagnetic Spectrum

The most important ideas summarized in figure 1.4 are:

  1. Electromagnetic waves span over many orders of magnitude in wavelength (or frequency).
  2. The frequency of the electromagnetic radiation is inversely proportional to the wavelength.
  3. The visible spectrum is a very small part of the electromagnetic spectrum.
  4. Photon energy increases as the wavelength decreases. The shorter the wavelength, the more energetic are its photons.